So why aren't there any beneficial infectious bacteria/viruses?

Then there are the countless viruses, or viral fragments, which have made their way into our DNA . They are presumably on the whole positive or they would have been selected against.

My question to the OP is: how do you know we don’t already have beneficial infections?

Don’t forget a lot of bacteria that do no harm but don’t help really CAN help us in a way.

Bacteria are living and they need food and room to move. Supposing you have a bunch of bacteria in your stomach that do no harm but do no good for you either.

Now suppose a bunch of evil bacteria find their way into your stomach. Now if since it’s full of benign bacteria (those germs that do no good or evil), these newly introduced “evil bacteria” have to compete with them.

But suppose there’s no food in your stomach for the “evil bacteria” because the benign bacteria have already eaten it up. Well these evil bacteria die. Supposing there’s no room for the “evil bacteria” to move, because the benign ones are taking up all the space.

The "evil guys’ then die. If it wasn’t for that benign bacteria there would be nothing to stop the bad germs from getting a hold, before the immune system could respond. This way, sometimes even germs that don’t hurt you or help you can have uses too

Or at least not evolutionarily harmful :smack:

The same way we find out that cold is caused by a virus and not evil influences. If every time someone gets a certain flu strain, they smell like pine trees, then we can investigate whether the flu causes the smell. Do we have any periodic beneficial effects that we have a need to explain?

Endogenous retroviruses may have a role in protecting the foetus from the maternal immune system. However, many EVRs have been deactivated by transcription errors and the like, and serve no practical purpose (except to supply additional DNA material into the genome that may be repurposed by mutation and selection over time).

Si

>Do we have any periodic beneficial effects that we have a need to explain?

Supposedly, there’s an immune system connection and general health. So getting a cold periodically may lead to not getting asthma or some other disease later in life because of a stronger immune system. So, its not exactly pine smell, but there may be non-obvious benefits to even the common cold and perhaps this is why our immune system never evolved to defeat a lot of these cold viruses: we simply were benefiting more from getting sick every so often.

That’s a somewhat more interesting question than it may appear. We’re highly motivated to research diseases and other things that make us feel bad. No one ever goes to the doctor to report that they’re feeling good for no reason, as Lister points out in the Red Dwarf episode. Certainly, no one’s researched feeling good nearly as much as feeling bad. I still don’t think it’s likely for reasons I explained before, but it’s always fun to speculate.

http://www.niams.nih.gov/News_and_Events/Press_Releases/1994/11_30.asp

Understand that the role of bacteria in many functions is just being discovered. Some arthritis is being linked with gut bacteria getting off balance, which could suggest that there were other bacteria keeping them at bay.

Lots. I feel particularly good every now and then for no obvious reason. Beneficial virus? No idea. Not interested in investigating whether it is either. But it could be, if it impelled me to contact more strangers and so pass is on.

vaccinia virus (cow pox) infection is a relativly harmless infection that used to protect against smallpox. Therefore, before the eradication of smallpox, you could have called a vaccinia virus infection beneficial.

Possibly, but you’d have to balance the benefit of smallpox immunity against the small percentage of people who got deathly ill or even died from the vaccinia virus itself.

I knew it, cats **are **plotting to take over. :slight_smile:

blink
WTF?!!

I remember reading about some parasite that infected a caterpillar and made it go up to the top of the grass stem and wait, so that it could get eaten by its next host, but this…?

In Jenner’s time, smallpox was indeed a major cause of dead, and vaccination a major progress (pdf)

You might possibly be interested in the subject of bacteriophages. http://en.wikipedia.org/wiki/Bacteriophage